This invention relates to air conditioning techniques and, more particularly, to solar air conditioning apparatus and method. The present subject matter is related to subject matter disclosed in the copending U.S. Patent Application Ser. No. 768,058 of W. E. Glenn et al., now U.S. Pat. No. 4,121,428 assigned to the same assignee as the present invention.
In recent years the high cost of conventional sources of energy has spawned numerous schemes for harnessing the sun's energy. However, a number of factors have prevented widespread adoption of solar energy systems. Many of the proposed schemes involve apparatus which is either complex or has expensive component materials, and even the prospect of virtually "free" energy from such systems after installation does not overcome the inordinate investment required to purchase and install the systems. Other schemes involve large-area collectors which are often either impractical due to their space requirements or are unsightly. Also, many of the proposed schemes have proved to be inefficient in operation in that they themselves require a substantial portion of the energy generated, such as to run moving parts.
One or more of the above-listed problems pervade existing solar energy schemes for producing heat or electricity, but the same problems are especially severe when attempting to utilize solar energy for air conditioning, since techniques to obtain cooling can tend to be particularly inefficient. Also, existing evaporative cooling systems typically require high pressure plumbing connections which can be disadvantageous. Notwithstanding these problems, the prospect of attaining a reasonably efficient and inexpensive solar air conditioning technique, especially in warm climates where anticipated year-round usage would justify substantial initial capital investment, is particularly attractive. As fossil fuel costs rise, the need for a practical solar air conditioning technique is increasingly felt, especially in such warm climates where air conditioning consumes a high percentage of total power company outputs.
In the copending U.S. Patent Application Ser. No. 768,058 of W. E. Glenn et al., there is disclosed a method and apparatus for cooling internal environment air using energy from the sun. In accordance with that invention, internal environment air is circulated over a desiccant to dry the internal environment air. The dried room air is cooled by performing a heat exchange operation with external environment air. Moisture is then added to the dried internal environment air which was subjected to the heat exchange operation. The desiccant is periodically heated with solar energy so as to remove moisture from the desiccant. The described cycle is repeated continuously.
The Glenn et al. technique has been found to operate successfully, but a problem arises when sufficient solar energy is not available to heat-dry the desiccant. It is an object of the present invention to provide a solution to this problem.